Electric vehicle battery lifetime optimization operational mode

ABSTRACT

A multi-mode operating system for an electric vehicle is provided, the system including means for a user to select a preferred mode of operation from a plurality of operational modes that include at least a Battery Life mode and a Standard mode, wherein the Battery Life mode is configured to select operating and charging parameters that emphasize battery health and battery life over vehicle range and/or vehicle performance. The system includes a thermal management system for maintaining the vehicle&#39;s battery pack to within any of a plurality of temperature ranges, and a charging system for charging the vehicle&#39;s battery pack to any of a plurality of minimum and maximum SOC levels and at any of a plurality of charging rates.

FIELD OF THE INVENTION

The present invention relates generally to batteries and, moreparticularly, to an electric vehicle operational mode that extends thelife of the cells within the vehicle's battery pack.

BACKGROUND OF THE INVENTION

Batteries can be broadly classified into primary and secondarybatteries. Primary batteries, also referred to as disposable batteries,are intended to be used until depleted, after which they are simplyreplaced with one or more new batteries. Secondary batteries, morecommonly referred to as rechargeable batteries, are capable of beingrepeatedly recharged and reused, therefore offering economic,environmental and ease-of-use benefits compared to a disposable battery.

Although rechargeable batteries provide a much longer service life thandisposable batteries, their service life is not unlimited. Dependingupon the type of battery, a rechargeable battery can typically berecharged anywhere from 100 times (e.g., alkaline) to 1000 times (e.g.,lithium-ion, lithium-polymer) to 20,000 times or more (e.g., thin filmlithium). In addition to depending upon the type of battery chemistryinvolved, the number of cycles that a rechargeable battery can berecharged depends on a variety of other factors that include; (i) therate of charging (i.e., slow trickle charge versus fast charge), (ii)the level of charging (i.e., 75% of full charge, full charge,over-charged, etc.), (iii) the level of discharge prior to charging(i.e., completely depleted, still charged to a low level, etc.), (iv)the storage temperature of the battery during non-use, and (v) thetemperature of the battery during use.

Due to the high initial cost of rechargeable batteries, expensiveproducts such as laptop computers often incorporate relativelysophisticated power management systems, thereby extending battery lifeand allowing the use of smaller, lower capacity batteries and/orbatteries that utilize less expensive cell chemistries. One of the mostcommon power management techniques is to place certain laptop componentsand peripherals, especially those that require relatively high levels ofpower to function, into either a standby mode or a low power usage modewhenever possible. Thus, for example, a laptop may provide two differentvideo screen brightness levels; high brightness when the computer isplugged in, and low brightness when the computer is operating on batterypower. This is also the primary purpose behind powering down the videoscreen when the computer is inactive for more than a short period oftime or placing wireless connectivity capabilities (e.g., Bluetooth,WiFi, WAN, etc.) or other non-essential peripherals in standby mode whenthey are not required.

A growing application for rechargeable batteries is that of electricvehicles. All-electric and hybrid vehicles, however, present a number ofengineering challenges, primarily due to the need for the rechargeablebattery pack of such a vehicle to meet the consumers' expectationsrelative to performance, range, reliability, lifetime and cost. Thepresent invention provides a battery pack management system that helpsachieve these goals.

SUMMARY OF THE INVENTION

A multi-mode operating system for an electric vehicle is provided, thesystem including means for a user to select a preferred mode ofoperation from a plurality of operational modes that include at least aBattery Life mode and a Standard mode, wherein the Battery Life mode isconfigured to select operating and charging parameters that emphasizebattery health and battery life over vehicle range and/or vehicleperformance. The system includes a thermal management system formaintaining the vehicle's battery pack to within any of a plurality oftemperature ranges, and a charging system for charging the vehicle'sbattery pack to any of a plurality of minimum and maximum SOC levels andat any of a plurality of charging rates.

In at least one embodiment, when the Battery Life mode is selected thesystem utilizes a maximum SOC level (e.g., 60% or less) during chargingthat is at least 10% lower than the maximum SOC level used when theStandard mode is selected; utilizes a maximum charging rate (e.g., C/20or less) that is lower than the charging rate used when the Standardmode is selected; and utilizes a maximum discharge rate (e.g., 1 C orless) that is lower than the maximum discharge rate used when theStandard mode is selected.

In at least one embodiment, when the Battery Life mode is selected thesystem utilizes a minimum SOC level during charging that is at least 5%higher than the minimum SOC level used when the Standard mode isselected; alternately, at least 15% higher than the minimum SOC levelused when the Standard mode is selected.

In at least one embodiment, when the Battery Life mode is selected thesystem utilizes a minimum loaded voltage set to a preset level ofapproximately 3.0 volts.

In at least one embodiment, during discharge the thermal managementsystem maintains the battery pack to a temperature within a first rangeof temperatures (e.g., 25° C. to 30° C.) when the Battery Life mode isselected, and within a second range of temperatures (e.g., 30° C. to 35°C.) when the Standard mode is selected.

In at least one embodiment, the maximum charge rate utilized when theBattery Life mode is selected depends on battery pack temperature,wherein the maximum charge rate is preset at C/20 or less if the batterypack temperature is above 10° C., and preset at C/50 or less if thebattery pack temperature is below 10° C.

In at least one embodiment, during discharge the thermal managementsystem maintains the thermal balance between cells within a first presetlimit (e.g., 5° C.) when the Battery Life mode is selected, and within asecond preset limit (e.g., 10° C.) that is greater than the first presetlimit when the Standard mode is selected.

In at least one embodiment, during an extended charging cycle thecharging system allows the battery pack to self-discharge to a firstminimum SOC level prior to re-initiating charging when the Battery Lifemode is selected, and to a second minimum SOC level prior tore-initiating charging when the Standard mode is selected, where thefirst minimum SOC level is at least 25% less than the second minimum SOClevel. The first minimum SOC level is preferably at least 30% less thanthe first maximum SOC level.

The means provided for the user to select the preferred mode ofoperation may utilize a touch screen, a plurality of switching means(e.g., push-buttons, toggle switches, rotating switches and slideswitches) with or without a display, a voice recognition system, an RFremote mode selector, and a remote mode selector communicating with avehicle communication interface over a network (e.g., internet).

In at least one embodiment, the system includes a mode indicator thatindicates to the vehicle's driver which mode has been selected.

A further understanding of the nature and advantages of the presentinvention may be realized by reference to the remaining portions of thespecification and the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 graphically illustrates the effects of charging cut-off voltageon battery life;

FIG. 2 graphically illustrates the effects of temperature on cellvoltage and discharge capacity;

FIG. 3 graphically illustrates cycle life degradation at differenttemperatures;

FIG. 4 graphically illustrates non-recoverable capacity loss due tostorage at high temperatures;

FIG. 5 graphically illustrates the effects of depth-of-discharge onbattery life;

FIG. 6 provides a system level diagram of the primary vehicle systemsimpacted and/or utilized by a battery pack system in accordance with theinvention;

FIG. 7 illustrates a touch-sensitive display screen associated with oneembodiment of a charging/operational mode selector;

FIG. 8 illustrates a touch-sensitive display screen similar to thatshown in FIG. 7, but utilizing a different set of modes;

FIG. 9 illustrates a non-touch-sensitive display used in conjunctionwith other switching means in an alternate embodiment of acharging/operational mode selector with similar control functionality tothat shown in FIG. 7;

FIG. 10 illustrates a charging/operational mode selector with similarcontrol functionality to that shown in FIG. 7 that does not require adisplay interface;

FIG. 11 illustrates a means for indicating the selectedcharging/operational mode;

FIG. 12 illustrates a system for remotely selecting the desiredcharging/operational mode; and

FIG. 13 illustrates a touch screen that may be used to set the presetvalues for the Optimal Battery Life operational mode.

DESCRIPTION OF THE SPECIFIC EMBODIMENTS

In the following text, the terms “battery”, “cell”, and “battery cell”may be used interchangeably and may refer to any of a variety ofdifferent cell types, chemistries and configurations including, but notlimited to, lithium ion (e.g., lithium iron phosphate, lithium cobaltoxide, other lithium metal oxides, etc.), lithium ion polymer, nickelmetal hydride, nickel cadmium, nickel hydrogen, nickel zinc, silverzinc, or other battery type/configuration. The term “battery pack” asused herein refers to multiple individual batteries contained within asingle piece or multi-piece housing, the individual batterieselectrically interconnected to achieve the desired voltage and capacityfor a particular application. The term “electric vehicle” as used hereinmay refer to an all-electric vehicle, also referred to as an EV, aplug-in hybrid vehicle, also referred to as a PHEV, or a hybrid vehicle,also referred to as a HEV, where a hybrid vehicle refers to a vehicleutilizing multiple propulsion sources one of which is an electric drivesystem.

FIGS. 1-5 illustrate several battery characteristics for an exemplarybattery pack. It should be understood that different battery packs, forexample those using a different cell chemistry, will exhibit differentprofiles than those shown in FIGS. 1-5, and that these figures are onlymeant to illustrate some of the issues involved with a typicalrechargeable battery.

FIG. 1 is a graph that illustrates the effects of charging cut-offvoltage on battery life, the cut-off voltage being the voltage at whichcharging is terminated. Utilizing a cut-off voltage of 4.15 volts (curve101), initially the battery pack achieves a higher capacity than thatobtained using a charge cut-off voltage of 4.10 volts (curve 103). Afterapproximately 200 charging cycles, however, the capacity of the batteryusing the lower charge cut-off voltage is greater than that of thebattery using the higher charge cut-off voltage, illustrating that theuseful lifetime of a battery pack can be dramatically extended by simplylowering charge cut-off voltage. Unfortunately lowering the chargecut-off voltage has consequences to other aspects of the battery pack'sperformance, in particular capacity, since a battery charged to a highervoltage exhibits a greater capacity than the same battery charged to alower voltage.

FIG. 2 is a graph illustrating the effects of temperature on the cellvoltage and discharge capacity of an exemplary battery. In the figure,curve 201 corresponds to a temperature of 40° C., curve 202 correspondsto a temperature of 30° C., and curve 203 corresponds to a temperatureof 20° C. As illustrated, an increase in operating temperature from 20°C. to 40° C. dramatically improves discharge capacity which, in turn,can lead to both improved vehicle performance (e.g., fasteracceleration) and improved driving range for an electric vehicle usingsuch a battery pack due to the lower impedance. A drawback, however, ofoperating at a higher temperature is the effect such a temperature hason battery life, specifically shortening the battery's cycle life.

FIG. 3 illustrates the effects of temperature on cycle life degradation.In this figure curve 301 corresponds to a battery pack cycled at 35° C.while curve 303 corresponds to a battery pack cycled at 55° C. As shown,by decreasing the storage temperature of a battery, it is able to retaina much higher capacity over a longer cycle life. FIG. 4 illustrates theeffects of temperature on energy retention for cells in storage, thedata taken for cells at a relatively high SOC (i.e., 4.2 volts). Curve401 corresponds to 20° C.; curve 403 corresponds to 40° C.; and curve405 corresponds to 55° C. Note the dramatic decrease as the storagetemperature is raised from 40° C. to 55° C.

There are many other battery characteristics that must be taken intoaccount during the design of the drive system, battery pack andattendant charging system of an all-electric or hybrid vehicle. Forexample, the depth of discharge which the system allows, or that thesystem is designed to accommodate, will affect a battery's life. Formost battery chemistries, frequently discharging the battery more than70 to 80 percent of rated capacity will lead to decreases in batterylife. This battery characteristic is shown in FIG. 5 which also showsthat discharges of only 20-30 percent will extend battery life. Inparticular, curve 501 corresponds to depth of discharge (DoD) of 10%;curve 502 corresponds to DoD of 20%; curve 503 corresponds to DoD of30%; curve 504 corresponds to DoD of 40%; curve 505 corresponds to DoDof 50%; curve 506 corresponds to DoD of 70%; and curve 507 correspondsto DoD of 100%.

FIG. 6 is a high-level view of a vehicle 600 and the primary vehiclesubsystems utilized and/or impacted by a vehicle control system designedto allow the user to select a battery lifetime optimization operationalmode for the vehicle in accordance with the invention. It will beappreciated that vehicle 600 can utilize other subsystem configurationswhile still retaining the multi-operational mode capabilities of thepresent invention. As shown, vehicle 600 includes a vehicle controlsystem 601 that monitors and controls the general operation of thevarious vehicle subsystems. System controller 601 is coupled to batterypack 603 and thermal management system 605. Thermal management system605, which preferably includes both a cooling subsystem 607 and aheating subsystem 609, is used to control battery pack temperature andis preferably coupled to other vehicle thermal systems, e.g., drivetrain cooling, passenger cabin HVAC system, etc., for example asdisclosed in co-assigned U.S. Pat. No. 7,789,176, and co-assigned andU.S. Patent Application No. 12/835,486, filed 13 Jul. 2010, now U.S. PatNo. 8,336,319, the disclosures of which are incorporated by referencefor any and all purposes. As described in further detail below,controller 601 preferably monitors the temperature of the cells withinbattery pack 603 using one or more sensors 611 and controls thetemperature of the battery pack using thermal management system 605 inorder to achieve the desired battery pack operating and/or storagetemperature.

In addition to monitoring battery pack temperature, vehicle controlsystem 601 also monitors the state of charge (SOC) of battery pack 603as well as the rate of battery discharge, both during vehicle operationand vehicle storage. In addition, in at least one embodiment system 601monitors and stores in on-board memory 613 the number of charging cyclesto which the battery has been subjected. Preferably for each chargingcycle the cut-off voltage and other charging parameters are monitoredand stored in memory 613, thereby providing information that can be usedto gauge the relative health of battery pack 603 throughout its expectedlifetime.

Control system 601 is coupled to a charging system 615 that controls andmonitors cut-off voltage during charging. Charging system 615 may alsocontrol and monitor the charge rate. Charging system 615 may either bean external system or integrated within vehicle control system 601. Inat least one embodiment, charging system 615 is external to both thecontrol system 601 and vehicle 600. In such an embodiment, preferablythe portion of the charging module that converts external power to apower level (e.g., voltage) that is compatible with battery pack 603 isexternal to the vehicle while a second portion of the charging modulethat controls charging characteristics such as cut-off voltage, chargingrate, etc. is internal to the vehicle. Alternately, the entire chargingmodule can be external to the power control subsystem 601 and thevehicle.

In at least one preferred embodiment, battery pack 603 is configured tobe plugged into, or otherwise connected to, an external power source 617via charging system 615. A municipal power grid is one example of anexternal power source 617. Charging system 615 insures that the powerfrom source 617 is converted to a form of power storable by battery pack603. For example, charging system 615 typically includes an AC to DCrectifier in order to convert power from the power source to thatrequired by battery pack 603. In at least one embodiment, battery pack603 is charged in whole or in part by a power generator 619 that iscontained within the vehicle, i.e., an on-board power generator, whichis coupled to the battery pack via charging system 615. It will beappreciated that in some embodiments, while external power source 617 ispreferred for providing a full charge to battery pack 603, internalpower source 619 can be used to augment the charge within the batterypack, for example by charging battery pack 603 during vehicle use,thereby extending driving range. In at least one embodiment, internalpower source 619 is a regenerative braking system.

Power control subsystem 601 also controls the power coupled from batterypack 603 to vehicle propulsion motor 621, for example using a powerelectronics module (PEM) 623. Power electronics module 623 is used toinsure that the power delivered to motor 621 has the desired voltage,current, waveform, etc. Thus, for example, PEM 623 preferably includes aDC to AC inverter, as well as the necessary control circuitry/processorto implement the various selectable modes as described in detail below.It will be appreciated that vehicle propulsion motor 621 can becomprised of a single electric motor or multiple electric motors.

User interface 625 is preferably integrated into the vehicle's userinterface, although interface 625 can be implemented in other ways asdescribed in detail below. Interface 625 provides a means for the userto control the selection of the vehicle's operational mode as well asassociated parameters. Preferably interface 625 also provides means foridentifying which mode the vehicle is in at any given time, as describedfurther below.

Vehicle Operational Modes

Conventional hybrid vehicles typically offer either two or three hybridoperational modes, i.e., modes in which the vehicle utilizes both theelectric motor and the combustion engine. If only two hybrid modes areoffered, typically the two modes are Economy and Power, the Economy modedesigned to enhance the fuel efficiency of the drive train, specificallyincreasing the miles per gallon of gasoline, while the Power modedelivers maximum performance. If a third mode is offered, typically itis a Normal mode in which the control system delivers performance andfuel efficiency that is somewhere between that provided in the Economyand Power modes. Note that many conventional hybrid vehicles may alsoprovide a full EV mode in which all propulsive power is provided by theelectric motor, although a typical hybrid can only drive a shortdistance in the EV mode, often with a dramatic reduction in bothallowable acceleration and top speed.

While a number of different approaches may be taken to achieve higherfuel efficiency in the Economy mode of a hybrid vehicle, typically inthis mode the vehicle control system will limit throttle response, thusachieving more fuel efficient acceleration. The control system may alsoswitch the passenger cabin climate control system to an energy-savingmode, for example a mode that modifies the load placed on the engine bythe air-conditioning system, as well as tuning the various electricsystem to reduce energy draw. Another technique that is often used toincrease fuel efficiency is to shift the transmission into a higher gearat lower rpms and/or lock the transmission's torque converter at lowspeeds. Lastly, in some vehicles the Economy mode provides feedback tothe driver in order to instigate more economical driving habits, forexample vibrating or increasing throttle pedal resistance if the controlsystem determines that the driver is attempting to accelerate above apreset rate.

As EVs only utilize an electric motor, or multiple electric motors, forpropulsive power, the various operational modes of an EV typicallyoperate quite differently than the modes in a hybrid vehicle. U.S. Pat.No. 7,671,567 describes four different modes for an EV, as well as theireffects on performance, range and battery life. The four described modesare standard, storage, extended driving range, and performance. Detailsfor each are provided below.

Standard Mode—In the Standard Mode, the system is configured to providethe optimal compromise between performance, driving range and batterylife. In general, the Standard Mode limits the cut-off voltage duringcharging to approximately 70%-95% of the rated capacity. Typically theStandard Mode maintains the battery pack at a relatively cooltemperature during both vehicle operation (i.e., driving) and whenplugged in, for example cooling the battery pack to a temperature withinthe range of approximately 30° C. to 35° C. during vehicle operation,and within the range of approximately 20° C. to 25° C. when the vehicleis plugged in to the external power source.

Storage Mode—The Storage Mode is configured to optimize battery lifewhen the vehicle is stored for an extended period of time, for example,for a period of time greater than 2 or 3 weeks. In this mode, thecut-off voltage during charging is limited to approximately 30%-70%, andmore preferably to approximately 30%-50%. As in the Standard Mode, thebattery pack temperature is maintained at a relatively cool temperature,preferably in the range of approximately 20° C. to 25° C. when thecharging system is coupled to an external power source. In suchconfigurations/vehicles, once the Storage Mode is selected, and assumingthat the vehicle is plugged in rather than operating and that thebattery pack's state of charge is greater than a preset value (e.g.,50%), the system actively lowers the charge state to the preset value,thereby helping to prolong battery life. In such a configuration, thesystem may actively lower the charge state by subjecting the batterypack to a load (e.g., turning on the lights or a fan or applying a dummyload).

Extended Driving Range Mode—This mode optimizes the system in order toachieve the maximum driving range, i.e., distance. During vehicleoperation, the battery is kept relatively warm, thereby decreasingbattery impedance and achieving greater discharge capacity. If theExtended Driving Range Mode is selected and the vehicle is plugged intoan external power source, typically the battery pack is cooled to alower temperature than normal and the maximum cut-off voltage is used,i.e., approximately 90%-100% of the rated capacity.

Performance Mode—This mode is intended to achieve the best vehicleperformance available, at the cost of both battery life and range.Therefore in this mode the maximum cut-off voltage is used duringcharging, i.e., approximately 90%-100%. Additionally, typically duringvehicle operation the battery pack temperature is maintained at a highertemperature than normal, e.g., within the range of approximately 37° C.to 40° C. Battery pack during charging is also maintained at atemperature that is higher than normal, e.g., within the range ofapproximately 35° C. to 40° C.

In the Performance Mode, the control system may also take other actionsto achieve superior performance, for example providing a temporaryincrease in the available current that can be supplied to motor 621.

In addition to the exemplary changes noted above that may be made basedon the selected operational mode, the controller may also be configuredto impact the charging profile, assuming the vehicle has some form of aninternal power generator 619 (e.g., regenerative braking system, solarpanels, etc.). In such a system, the state of charge of the battery packmay be monitored and maintained within a predefined range using thecharging capabilities provided by the internal power generator. Forexample, in the Standard Mode an average charge of approximately 50% maybe maintained; in the Storage Mode an average charge of 30-50% may bemaintained; and in the Extended Range and the Performance Modes anaverage charge of approximately 70% may be maintained.

Optimal Battery Life Mode

Each of the operational modes described above is intended to respond toa specific user concern or desire for a particular vehicle. For example,the Economy mode attempts to achieve the best possible fuel economy; theExtended Range mode attempts to achieve the longest driving distance,thereby helping to alleviate range anxiety; and the Performance Modestrives to provide the best possible performance, i.e., acceleration andtop speed. None of these modes, however, overcomes the anxiety ofelectric vehicle owners or the fear of potential buyers that they willhave to replace the battery pack in their vehicle sooner than expected,or that they are potentially harming the battery pack and its lifetimethrough their manner of operating or charging their car. Accordingly,the present invention overcomes these concerns by providing anoperational mode that maximizes battery life, even if that choice limitsdriving range, fuel economy and/or performance.

In accordance with the invention, the user of an electric vehicle 600 isable to select an Optimal Battery Life mode utilizing user interface625. Both pure electric vehicles, i.e., EVs, and hybrid vehicles may beconfigured to provide such an operational mode. Once selected, vehiclesystem controller 601 sets a number of operational parameters of thevehicle in accordance with preset values for each of the operationalparameters. Preferably the preset values are set by the vehicle'smanufacturer, although the system may also be configured to allowvehicle dealers, third parties (e.g., repair shops), and/or thevehicle's owner to set and/or adjust the preset values.

The parameters set through selection of the Optimal Battery Life modewill vary depending upon the specifics of the vehicle in question, forexample, battery chemistry, thermal control system capabilities,charging system configuration, etc. In general, however, the system willcontrol one or more of the following parameters. It should be understoodthat the recommended preset values for each of the exemplary parametersassumes a certain type of battery, e.g., lithium ion battery chemistry,and therefore other preset values may be used for other systems.

SOC—The minimum and maximum SOC levels are preferably set when thesystem is operating in the Optimal Battery Life mode. In an exemplaryembodiment, a minimum SOC level of 15% and a maximum SOC level of 60%are set by selection of this mode. Typically the minimum SOC level inthis mode is set at a value that is at least 5% higher than the minimumSOC level set in the Standard Mode, and the maximum SOC level in thismode is set at a value that is at least 10% lower than the maximum SOClevel set in the Standard Mode.

Minimum Loaded Voltage—In at least one embodiment of the invention, whenthe Optimal Battery Life mode is selected, a minimum loaded voltage isset for the cells within battery pack 603. For example, in oneconfiguration the minimum loaded voltage is set to a preset value of 3.0volts.

Battery Temperature During Discharge—Another parameter that may be setwhen the Optimal Battery Life mode is selected is the batterytemperature during discharge (i.e., vehicle operation). For example, inat least one embodiment the battery pack is maintained within atemperature range of approximately 30° C. to 35° C. during discharge;alternately, to a temperature within the range of approximately 25° C.to 30° C. during discharge.

Battery Temperature During Charging—In addition to setting dischargetemperatures, preferably when the Optimal Battery Life mode is selectedthe system also sets the battery temperature to be maintained duringcharging, the temperature selected to minimize degradation duringcharging. In at least one embodiment, the preset temperature for thismode of operation is within the range of 35° C. to 40° C. It will beappreciated that in a typical scenario, battery heating (for exampleusing heating system 609) will be required in order to raise thetemperature of the battery pack to the preset charging temperature.

Battery Temperature During Storage—In addition to setting charge anddischarge temperatures, preferably when the Optimal Battery Life mode isselected the system also sets the battery temperature to be maintainedduring storage. In at least one embodiment, during storage the batterypack is maintained at a temperature within the range of approximately15° C. to 20° C.; alternately, to a temperature within the range ofapproximately 20° C. to 25° C.

SOC During Storage—As noted above, preferably the minimum and maximumSOC levels are set when the system is operating in the Optimal BatteryLife mode. An additional SOC level may be set in this mode when thevehicle enters into periods of storage. Typically storage periods areset by the user, for example via user interface 625. Storage periods maybe set on a one-by-one basis, or as a series of events (e.g., every weekfrom 11:00 PM Friday through 11:00 PM Sunday. In at least oneembodiment, the maximum SOC level during storage is set at 50% SOC;alternately, to a level of 40% SOC; alternately, to a level of 30% SOC.Preferably if the Optimal Battery Life mode includes this parameter,system controller 601 also includes means for insuring that the batteryis charged to a higher SOC (e.g., 60%) prior to vehicle use. Forexample, in at least one configuration the user is able to set, via userinterface 625, an intended drive time (e.g., day/date and time).Controller 601 then charges battery pack 603 to the higher SOC level(e.g., 60%) immediately prior to this day/date and time so that thevehicle is charged to the highest level allowed by the selectedoperational mode prior to its use.

Maximum Charge Rate—Preferably if the Optimal Battery Life mode isselected, the system sets the maximum allowable charge rate to arelatively low rate, thus maximizing battery health. In an exemplaryconfiguration, the maximum allowable charge rate is set to C/20.

Maximum Charge Rate as a Function of Temperature—In addition to simplysetting the maximum charge rate, the system may also be configured toset the maximum allowable charge rate as a function of batterytemperature. For example, in one configuration a maximum allowablecharge rate of C/20 or less is set if the battery is within atemperature range of 20° C. to 25° C.; a maximum allowable charge rateof C/30 or less is set if the battery is within a temperature range of15° C. to 20° C.; a maximum allowable charge rate of C/40 or less is setif the battery is within a temperature range of 10° C. to 15° C.; and amaximum allowable charge rate of C/50 or less is set if the battery isat a temperature of 10° C. or less. In an alternate example, a maximumallowable charge rate of C/20 or less is set if the battery temperatureis higher than 10° C., and to a maximum allowable charge rate of C/50 orless if the battery temperature is lower than 10° C.

Maximum Charge Rate as a Function of Charging Time—In addition to simplysetting the maximum charge rate or setting the charge rate as a functionof battery temperature, the system may also be configured to set themaximum allowable charge rate as a function of allowed charging time. Ingeneral, in this configuration the user inputs information that thesystem controller 601 can use to determine the allowable charging time.After determining the allowable charging time, controller 601 determinesthe charge rate necessary to charge the battery pack to the maximumallowed SOC, preferably preset when the Optimal Battery Life mode isselected, within the allowed time. The information input by the user maybe the next expected drive time (e.g., day/date/time). Alternately, theinformation may be the allotted charging time (e.g., 8 hours).

Battery Pack Thermal Balance During Discharge—Preferably the thermalbalance of the batteries within pack 603 during discharge is monitoredand maintained within a preset limit. For example, while the thermalbalance between cells of the pack during normal vehicle operation may beset to a level of less than 10° C., preferably when the Optimal BatteryLife mode is selected a thermal balance of less than 5° C. ismaintained.

Maximum Discharge Rate—Preferably if the Optimal Battery Life mode isselected, the system sets the maximum allowable discharge rate, thisdischarge rate being set to a value that is at, or above, the minimumrate necessary to provide the driver with sufficient power to drivesafely. For example, for a particular vehicle/battery pack, a maximumdischarge rate of between 1 C and 2 C may be allowed during normaloperation, but that rate may be set at a maximum rate of 0.5 C when theOptimal Battery Life mode is selected. In this example, if theparticular vehicle/battery pack requires that a discharge rate of atleast 0.7 C be available to meet safe driving standards for thatvehicle, then the maximum rate of 0.7 C, rather than 0.5 C, would beused as the preset maximum discharge rate when the Optimal Battery Lifemode is selected.

Extended Charging—Occasionally a vehicle may be connected to thecharging source (e.g., garage power socket) for an extended period oftime, for example throughout the week/weekend or while the owner istraveling. In a conventional electric vehicle left in this situation,the charging system will typically maintain the battery at or near thepreset SOC level, e.g., 90% SOC. In the present system when the OptimalBattery Life mode is selected, this parameter allows the battery toself-discharge to a much lower rate before re-initiating the chargingcycle, thereby limiting the frequency that the battery is recharged whenleft coupled to the charging source. For example, in one configurationafter the battery pack is charged to an upper preset value, e.g., 60%SOC, the battery is allowed to self-discharge to a lower preset value,e.g., 15% SOC, before recharging. Preferably the range between the upperand lower preset values is at least 20%; alternately, at least 30%;alternately, at least 40%. Preferably if this parameter is set in theOptimal Battery Life mode, the system is also configured to set themaximum charge rate as a function of allowed charging time as describedabove, thus insuring that the vehicle is charged to or near the upperpreset value when the user wants to drive the vehicle, and that thecharging rate used to achieve that SOC level does not exceed a presetcharge rate.

Mode Selection

The present invention can utilize any of a variety ofcharging/operational mode selection means. In a preferred embodiment, adisplay system is used, either alone with a touch-sensitive screen, ortogether with a plurality of switching means (e.g., toggle switches,push button switches, slide switches, etc.). For example, FIG. 7illustrates a portion of a touch-sensitive touch screen 700 whichincludes a plurality of touch-sensitive buttons 701-705 that correspondto various available charging/operational modes. FIG. 8 illustrates asimilar screen portion 800 that includes a different set oftouch-sensitive buttons 801-804 that correspond to variouscharging/operational modes more likely to be found in a hybrid vehicleutilizing the Optimal Battery Life mode of the invention. The displaysshown on screens 700 and 800 may be located on a dedicated screen.Alternately and as preferred, the displays shown on screens 700 and 800may be one of a plurality of available displays (i.e., menus) that auser may access on the user interface (e.g., interface 625). In thepreferred embodiment, in addition to the mode selector display, avariety of other menus/displays may be presented, e.g., vehicleperformance, battery performance, battery SOC, available driving range,passenger cabin HVAC controls, audio entertainment controls, cell phonecontrols, navigation system controls, etc.

In screens 700 and 800, touching one of the buttons 701-705/801-804causes the corresponding mode to be selected. Preferably the touchedbutton is highlighted to indicate the selection. For example, button 702is highlighted in FIG. 7 and button 804 is highlighted in FIG. 8. In analternate embodiment, a mode selection button must be touched followedby pushing (i.e., touching) a data entry button 707. Requiring theselection of two buttons, i.e., the mode button and the entry button,decreases the risk of an inadvertent mode change. In an alternateembodiment that is intended to further reduce the risk of inadvertent orunauthorized mode changes, after selecting a mode, or after selecting amode and touching the data entry button, a secondary mode selectionscreen is displayed (not shown) that requests a user personalidentification number (PIN) or password.

As previously noted, the present invention is not limited to a singlemeans for inputting the desired mode. For example, if anon-touch-sensitive display is used, preferably the screen isimmediately adjacent to a plurality of buttons, toggle switches, orother switching means that are used in conjunction with the display toprovide the selection means. FIG. 9 illustrates such a mode selectorsystem 900 that includes the same functionality as provided bytouch-screen 700. As shown, screen 901 is configured so that thepossible modes 903-907 as well as other possible inputs (e.g., entrybutton 909) are immediately adjacent to hard buttons, or other switchingmeans, 911-916. It will be appreciated that the hard buttons (e.g.,buttons/switches 911-916) can be used to provide other data input simplyby re-configuring the display and associating the hard switches 911-916with other functions.

In addition to a charging/operational mode selector that uses a displayscreen, a simple non-display mode selector can also be used with theinvention, for example a mode selector comprised solely of push buttons,toggle switches, slide switches, rotating switches, etc. Such a modeselector may be located within the passenger compartment (e.g., on thedash, on the console, etc.) or elsewhere (e.g., near the plug-inreceptacle on the outside of the vehicle, preferably covered by acharging receptacle cover door). FIG. 10 illustrates one suchcharging/operational mode selector that does not require a displayinterface, rather it uses a rotating switch 1001. Indicators 1003surround switch 1001, each of which indicates a particularcharging/operational mode. In the illustration shown in FIG. 10, fivecharging/operational modes are shown with the Optimal Battery Life Mode,labeled “Battery Life”, selected.

In another embodiment, the charging/operational mode selection meansuses a voice recognition system such as those commonly used withon-board vehicle navigation systems. Preferably the voice recognitionsystem uses a display interface as well, thus simplifying system/userinteraction and providing the user with positive indicators when theirvoice inputs have been correctly accepted by the system.

Regardless of the selection means used, preferably the system includesone or more indicators that indicate the selected mode. Preferably theindicators are easily visible to insure that the user recognizes theselected mode. For example, five indicators can be located on thedashboard, easily visible to the driver, representing the fivecharging/operational modes illustrated in FIGS. 7, 9 and 10(alternately, four indicators representing the four modes illustrated inFIG. 8). Preferably next to each indicator is either a textual indicatorof the mode, as shown in FIG. 11, or a symbolic indicator of the mode.In at least one embodiment, the indicators are also color coded, thusproviding a secondary indicator of selected mode. For example, in theindicators shown in FIG. 11, indicator 1101 is blue, indicator 1102 isgreen, indicator 1103 is white, indicator 1104 is yellow and indicator1105 is red. This is but one of numerous ways in which the selected modecan be highlighted to the driver of the vehicle.

In addition to, or instead of, an on-board charging/operational modeselection means, a remote selection means can be employed. The primaryadvantage of this type of mode selector is that it allows the user toremotely alter the charging/operational mode. For example, while on atrip the user may find that their trip has been extended and that theirvehicle will not be used for an extended period of time and as such,would like to change the mode of the vehicle to the Storage Mode,thereby improving battery life. In an alternate example, a user may findthat the next day's travel will be much further than normal. In thisscenario the user may wish to change from a Battery Life mode to a MaxRange mode. Certain types of remote mode selectors would allow the userto change the mode as required, without the need for being in or next tothe vehicle.

FIG. 12 is a simplified illustration of a system for remotecharging/operational mode selection. As shown, the system includes aremote mode selector 1201 and an on-board communication system 1203 thatcommunicates with remote mode selector 1201 via communication network1205. On-board communication system 1203 is coupled to on-board modeselection means 1207, both of which are contained within vehicle 1209.In the simplest form, remote mode selector 1201 is an RF remote,therefore not requiring a communication network. Due to the limitedrange of an RF remote, in a preferred embodiment remote 1201communicates via network 1205, network 1205 being any of a variety ofknown network systems such as cellular, internet, satellite or other.For example, in one embodiment the remote mode selector 1201 is acomputer or an application on a cell phone and network 1205 is aninternet-based network system. Further descriptions of suitable vehiclecommunication systems are given in co-assigned U.S. Pat. No. 7,698,078,issued 13 Apr. 2010, the disclosure of which is incorporated herein forany and all purposes.

In at least one embodiment of the invention, the system prompts the userto select a charging/operational mode. For example, in one configurationthe user is prompted after turning off the car, but prior to exiting thecar, for example when the user first turns the key (or other vehicleon/off control switch) from the operational/driving position to thestandby/off position. The user can be prompted by a tone or series oftones, by a pre-recorded or synthesized voice, or by a display means(e.g., flashing indicator, flashing screen on the display interface,etc.), or a combination thereof.

In addition to selecting the desired charging/operational mode, in atleast one embodiment the user is also able to set at least some of theparameters employed in the Optimal Battery Life mode. In order to insurethat the settings are still useful from the stand-point of optimizingbattery life, preferably the user is given a very limited range for anyparameter that they are allowed to set. Additionally, while the user maybe allowed to set some of the parameters, typically other battery lifeparameters are set without user input, once the user selects the OptimalBattery Life mode. For example, while the user may be allowed to set SOClevels, charging rates and temperatures may be set in accordance with apreset set of instructions input by the manufacturer or an authorizedthird party, thus insuring that this mode still achieves its goals ofimproving battery life.

FIG. 13 illustrates this aspect of the invention, this figure providingan exemplary touch screen 1300 that allows the user to set minimum SOC1301, maximum SOC 1303, maximum discharge rate 1305 and the batterytemperature during discharge 1307. In this example, specific values forsome of the parameters can be set by the user (e.g., 1301 and 1303),while other parameters only allow the user to select relative values(e.g., low, medium and high). In the illustrated embodiment, as the usermakes a selection an indicator 1309 moves on range scale 1311, thusproviding the user with feedback as to how their selection will impactthe vehicle's driving range. Similarly, an indicator 1313 shows theimpact relative to vehicle performance scale 1315. Lastly, in thisexample an indicator 1317 shows how the user's selections impact batterylife on battery life scale 1319. It should be understood that screen1300 only represents an exemplary embodiment and that the invention mayor may not provide the user with means for setting the parametersapplied when the Optimal Battery Life mode is selected; that the meansfor setting such parameters may include means other than a touch screen(e.g., hard buttons/dials, computer interface, web-based applications,etc.); and that the parameters that may be set in this manner mayinclude a different set of parameters than those illustrated.

It should be understood that identical element symbols used on multiplefigures refer to the same component, or components of equalfunctionality. Additionally, the accompanying figures are only meant toillustrate, not limit, the scope of the invention and should not beconsidered to be to scale.

Systems and methods have been described in general terms as an aid tounderstanding details of the invention. In some instances, well-knownstructures, materials, and/or operations have not been specificallyshown or described in detail to avoid obscuring aspects of theinvention. In other instances, specific details have been given in orderto provide a thorough understanding of the invention. One skilled in therelevant art will recognize that the invention may be embodied in otherspecific forms, for example to adapt to a particular system or apparatusor situation or material or component, without departing from the spiritor essential characteristics thereof. Therefore the disclosures anddescriptions herein are intended to be illustrative, but not limiting,of the scope of the invention which is set forth in the followingclaims.

What is claimed is:
 1. A multi-mode operating system for an electricvehicle, comprising: a battery charging system for charging a batterypack of said electric vehicle, wherein said battery charging systemcharges said battery pack to any of a plurality of maximum and minimumstate-of-charge (SOC) levels, and wherein said battery charging systemcharges said battery pack using any of a plurality of charging rates; athermal management system coupled to said battery pack of said electricvehicle, wherein said thermal management system maintains said batterypack to within any of a plurality of temperature ranges; a vehiclecontrol system coupled to said battery charging system and to saidthermal management system; and means for selecting a vehicle operatingmode from a plurality of operational modes controlled by said vehiclecontrol system, wherein said plurality of operational modes includes atleast a Battery Life mode and a Standard mode, wherein said selectingmeans is accessible by a user of said electric vehicle, wherein saidBattery Life mode utilizes a first maximum SOC level during battery packcharging that is at least 10% lower than a second maximum SOC levelutilized in said Standard mode, wherein said Battery Life mode utilizesa first maximum charge rate and said Standard mode utilizes a secondmaximum charge rate that is higher than said first maximum charge rate,wherein said Battery Life mode utilizes a first maximum discharge rateand said Standard mode utilizes a second maximum discharge rate that ishigher than said first maximum discharge rate.
 2. The multi-modeoperating system of claim 1, wherein said first maximum SOC level ispreset at 60% or less, wherein said first maximum charge rate is presetat C/20 or less, and wherein said first maximum discharge rate is presetat 1C or less.
 3. The multi-mode operating system of claim 1, whereinsaid Battery Life mode utilizes a first minimum SOC level during batterypack charging that is at least 5% higher than a second minimum SOC levelutilized in said Standard mode.
 4. The multi-mode operating system ofclaim 1, wherein said Battery Life mode utilizes a first minimum SOClevel during battery pack charging that is at least 15% higher than asecond minimum SOC level utilized in said Standard mode.
 5. Themulti-mode operating system of claim 1, wherein said Battery Life modeutilizes a minimum loaded voltage set to a preset level of approximately3.0 volts.
 6. The multi-mode operating system of claim 1, wherein saidthermal management system maintains said battery pack during dischargeto a first temperature within a first range of temperatures when saidBattery Life mode is selected, wherein said thermal management systemmaintains said battery pack during discharge to a second temperaturewithin a second range of temperatures when said Standard mode isselected, and wherein said first range of temperatures is less than saidsecond range of temperatures.
 7. The multi-mode operating system ofclaim 6, wherein said first range of temperatures is approximately 25°C. to 30° C., and said second range of temperatures is approximately 30°C. to 35° C.
 8. The multi-mode operating system of claim 1, furthercomprising at least one battery pack temperature sensor, wherein saidfirst maximum charge rate utilized when said Battery Life mode isselected depends on a battery pack temperature, wherein said firstmaximum charge rate is preset at C/20 or less if said battery packtemperature is above 10° C., and wherein said first maximum dischargerate is preset at C/50 or less if said battery pack temperature is below10° C.
 9. The multi-mode operating system of claim 1, wherein duringdischarge said thermal management system maintains a thermal balancebetween a plurality of cells comprising said battery pack within a firstpreset limit when said Battery Life mode is selected and within a secondpreset limit when said Standard mode is selected, and wherein said firstpreset limit is less than said second preset limit.
 10. The multi-modeoperating system of claim 9, wherein said first preset limit isapproximately 5° C. and said second preset limit is approximately 10° C.11. The multi-mode operating system of claim 1, wherein during anextended charging cycle said battery charging system allows said batterypack to self-discharge to a first minimum SOC level prior tore-initiating charging when said Battery Life mode is selected and to asecond minimum SOC level prior to re-initiating charging when saidStandard mode is selected, wherein said first minimum SOC level is atleast 25% less than said second minimum SOC level.
 12. The multi-modeoperating system of claim 11, wherein said first minimum SOC level is atleast 30% less than said first maximum SOC level.
 13. The multi-modeoperating system of claim 1, wherein said selecting means is comprisedof a touch-sensitive screen.
 14. The multi-mode operating system ofclaim 1, wherein said selecting means is comprised of a display systemand a plurality of switching means.
 15. The multi-mode operating systemof claim 14, wherein said switching means are selected from the groupconsisting of push-buttons, toggle switches, rotating switches and slideswitches.
 16. The multi-mode operating system of claim 1, wherein saidselecting means is comprised of a plurality of switching means.
 17. Themulti-mode operating system of claim 1, wherein said selecting means isa voice recognition system.
 18. The multi-mode operating system of claim1, further comprising a communication interface in communication with anetwork, wherein said selecting means is a remote mode selector incommunication with said network, wherein said remote mode selector isseparate from said electric vehicle.
 19. The multi-mode operating systemof claim 1, further comprising an RF communication interface, whereinsaid selecting means is an RF remote mode selector separate from saidelectric vehicle.
 20. The multi-mode operating system of claim 1,further comprising at least one mode indicator, wherein said at leastone mode indicator indicates which mode of said plurality of operationalmodes is selected by said selecting means.